The present disclosure relates to plastic containers. More particularly, it relates to thermoformed containers for containing food products.
One area where the use of plastic containers has become wide spread is in the food packaging industry. Accordingly, it is common for these plastic food containers to serve as the end display package in which the food product is presented for sale to the customer. Typical of these containers are those used for dairy products such as cottage cheese, sour cream, or the like where an integral body of the container is provided having a side wall that tapers down from a larger diameter top opening to an integral, transverse bottom wall, with the top opening being closed by a separate, plug-fit lid. Normally, the lid has a depending peripheral skirt that locks onto an upper rim of the tapered wall of the container body.
A somewhat related plastic food container design currently used for flavored yogurt provides a reverse tapered side wall main body or sleeve forming a smaller diameter top opening and a large diameter bottom opening. A separate bottom closure member closes off the bottom opening so that yogurt (or other food product) can be received and contained within the main body. The bottom closure member includes a base panel and a depending skirt wall that is attached (e.g., spinwelded) to the interior surface of the main body to permanently attach the pieces to one another. Thus, unlike the previously described top closure lids that are designed to be opened (i.e., removed from the larger diameter opening of the container), the bottom closure for this particular yogurt container does not have a locking skirt that otherwise locks onto a rim of the side wall and that can be opened to gain access to the food therein. Instead, the bottom closure is affixed to the main body and after being filled with yogurt, the top opening is closed by a flexible foil seal adhered to a lip of the main body. To gain access to the yogurt, the seal is peeled away from the top opening.
Regardless of a final shape, in some instances, food product plastic containers have their parts formed by a thermoforming process. In thermoforming, a thin plastic sheet is formed into the desired shape by heating and forcing the sheet against a mold to produce a container part having a uniform, very thin cross-sectional thickness that can result in a part having very flexible walls. For example, the yogurt container described above was originally manufactured by thermoforming the main body and bottom closure, and then spinwelding the components to effectuate a permanent attachment. In an effort to address perceived concerns associated with these prior thermoformed and spinwelded yogurt containers, an injection molded construction was devised and is described, for example, in U.S. Pat. No. 6,213,301. In general terms, the '301 patent describes a two-piece, injection molded plastic container in which an injection molded frustoconical main body portion is ultrasonically welded to an injection molded lower body portion (serving as a bottom closure member). Ribs are formed on an exterior of the main body portion, and facilitate consistent, spaced stacking of multiple main body portions to one another, such as during shipping and/or within high speed automated feeding equipment. Similarly, internal ribs are formed along the lower portion, and facilitate desired spaced stacking thereof.
While the injection molded plastic containers of the '301 patent are highly viable, opportunities for improvement remain. For example, with injection molding, a relatively significant quantity of plastic resin is required in order to achieve desired container stiffness. Further, gate markings inherent to injection molded parts can hamper various production steps, such as when attempting to uniformly adhere the foil seal to the lip.
In light of the above, a need exists for an improved food product container.